The present invention relates to a sheet transportation and separation apparatus. The sheet transportation and separation apparatus is used for separating a sheet, which is transported in close contact with the surface of a member moving in one direction, and is usually applied to image reproducing apparatuses such as copying machines and facsimile devices.
Such image reproducing apparatuses, for example electrophotographic copying systems of various types, using image transfer processes are, as is well-known, roughly classified into a visible image transfer type in which latent electrostatic images are formed on the surface of an image bearing member, for example, a photoconductor or a dielectric material, and the latent electrostatic images are then developed into visible images, which are thereafter transferred to an image transfer material; and an electrostatic latent image transfer type in which the latent electrostatic image formed on the surface of an image bearing member as mentioned above are transferred to an image transfer material having a dielectric surface, and then the transferred latent electrostatic images are developed into visible images.
In either type of image transfer mentioned above, the process of separating an imge transfer material from the image bearing member, which material is transported in uniform contact with the surface of the image bearing member is very important. Various types of image transfer material separation apparatuses with the above-mentioned function have been proposed and provided for practical use.
There is known a pick-off belt separation system which is one of the conventional image transfer material separation apparatuses. In this system, a pick-off belt made of a thin material is in contact with the peripheral surface of one side of an image bearing member, which can be in a drum or an endless belt shape. One side of the image transfer material, fed so as to be brought into close contact with the image bearing member, is caused to run over the above-mentioned pick-off belt, i.e., the pick-off belt is placed between the surface of the image bearing member and the image transfer material during the separation process. The pick-off belt extends parallel to the movement direction of the image bearing member and to the movement direction of the image transfer material. The opposite side ends of the pick-off belt are positioned away from the surface of the image bearing member.
Therefore, one side of the image transfer material is in close contact with the images formed on the surface of the image bearing member for image transfer, and the side portion rides on the pick-off belt from the beginning, and, with continuous transfer of the image transfer material, the image transfer material is moved away from the surface of the image bearing member.
This pick-off belt separation system can separate the image transfer material from the surface of the image bearing member without fail after image transfer, since one side portion of the image transfer material is separated from the surface of the image bearing member from the beginning by the pick-off belt. In this sense, the pick-off belt separation system is one of the best conventional image transfer material separation systems. However, that system has the following unavoidable shortcoming:
In the system, the one side portion of the image transfer material which rides onto the pick-off belt does not come into contact with the surface of the image bearing member, and therefore no images can be formed in the one side portion of the image transfer material, forming a blank portion in the transportation direction of the image transfer material.
In the pick-off belt system, this shortcoming is unavoidable, and when images exist in the very side portion of the original document, part of the images in the side portion cannot be duplicated. Stated differently, the side edge portion is the so-called dead space or pick-off margin, which is a big obstacle to increasing the effective image area on the image bearing member.
In order to remove the above-mentioned shortcoming, an image transfer material separation apparatus has been proposed in U.S. patent application Ser. No. 219,258 filed Dec. 22, 1980 which is a continuation-in-part of U.S. patent application Ser. No. 213,650 filed Dec. 5, 1980 now abandoned. This apparatus can guarantee the same performance as the conventional image transfer material separation apparatus employing the pick-off belt, and can maximize the effective image area on the image bearing member. In this systemm, a corner of the image transfer material in the leading edge side thereof is bent or curled so as to be separated from the surface of the image bearing member. Furthermore, a corner separator, which is substantially triangular in shape and has an image transfer material separation vertex, is positioned so as to be in light contact with or in close proximity with the surface of the image bearing member. The corner separator catches the above-mentioned folded or curled portion of the image transfer material and separates the transfer material from the surface of the image bearing member.
One of the significant shortcomings of this system is that an apparatus for folding the corner of the image transfer material in timed relation with the transportation of the transfer material is required. Such an apparatus is extremely complex in mechanism and expensive.
Furthermore, the above shortcoming is inevitable in devices such as a facsimile and an image reproducing apparatus employing a sheet transportation and separation apparatus, which separates a sheet closely contacted to the surface of a member moving in one direction.